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Physio > Autonomic Nervous System > Flashcards

Autonomic Nervous System Flashcards

1
Q

ANS functions

A

. Innervates smooth muscle, heart and glands
. AP in nerve can result in excitation or inhibition of effector cells
. Autonomic reflexes control organ function
. 2 neurons btw CNS and effector organ
. Slower conduction: longer, less focused response

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2
Q

SNS functions

A 
. Innervates skeletal muscle 
. AP in nerve always results in contraction of skeletal muscle 
. Under voluntary control 
. 1 neuron btw CNS and muscle 
. Faster conduction, focused response
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3
Q

ANS divisions

A

. sympathetic
. Parasympathetic
. Enteric
. Maintain homeostasis

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4
Q

Single innervation target organs

A 
. Sweat glands 
. Peripheral blood vessels 
. Hair follicles 
. Brown adipose 
. Adrenal medulla 
. Kidney
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5
Q

Dual innervation target organs

A 
. Eye 
. Salivary glands
. Lung
. Heart
. Enteric nervous system 
. Pancreas
. Liver
. Bladder
. Reproductive organs 
. Blood vessels of external genitalia
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6
Q

SNS

A

. Thoracolumbar
. Preganglionic axons leave in ventral root, enter paravertebral ganglion through white rami
. Go through paravertebral or prevertebral ganglia (1 plexus in front of aorta)
. Preganglionic fibers synpase w/ postganglionic neurons or travel for several segments before forming synapses w/ postganglionic neurons
. Postganglionic axons leave ganglia through gray communicating rami to enter spinal n.
. Prevertebral plexus forms by celiac, sup., and inf. Mesenteric ganglia

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7
Q

PNS

A

. Craniosacral
. Preganglionic cell bodies in nuclei of brain stem and S2-4
. Preganglionic fibers from upper nuclei distribute w/ 4 cranial nn (III, VII, IX, and X) and from sacral segments go w/ sacral nn.

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8
Q

Autonomic reflexes

A

. Afferent neurons activated by stimulus
. Afferent signal integrated in CNA
. Efferent autonomic neurons activated to modulate target organ function in response to initial stimulus
. Afferent and efferent neurons may innervates the same or different organs
. Efferent arm has preganglionic (in peripheral ganglia) and postganglionic neuron (to target organs w/ varicosities along it’s length to release neurotransmitter)

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9
Q

PNS functions

A 
. Contract pupil 
. Inc. secretions 
. Enhance GI motility
. Stimulate insulin release 
. Slow HR
. Constrict airway 
. Vasodilate vessels
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10
Q

SNS functions

A 
. Dilate pupil 
. Dec. GI motility 
. Stimulate gluconeogenesis, inhibit insulin
. Inc. HR
. Inc. arterial pressure 
. Dilate bronchial smooth muscle 
. Inc. blood flow to muscle, dec. blood to abdominal organs 
. Whole body sweating
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11
Q

ACh neurotransmitters

A

. Cholinergic nn.
. All sympathetic and parasympathetic preganglionic nn.
. Only sympathetic sweat gland postganglionic
. All parasympathetic postganglionic

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12
Q

NE neurotransmitter

A

. Adrenergic
. All sympathetic postganglionic except sweat glands
. Adrenal medulla releases some into bloodstream

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13
Q

epinephrine

A

. Released from adrenal medulla after activation of SNS

. Catecholamine

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14
Q

ACh synthesis

A

. Choline + acetate -> acetyl CoA + CoA -> ACh

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15
Q

NE synthesis

A

. Tyr -> DOPA -> dopamine -> NE -> E

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16
Q

Characteristics of receptor-neurotransmitter interaction

A

. Threshold: conc. Of NT where response 1st occurs
. Saturation
. Specificity
. Sensitivity: conc. NT to elicit 50% max response
. Potency: ligand conc. To achieve max response
. Competition
. Agonist
. Antagonist

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17
Q

Magnitude of biological response to a ligand depends on ____

A

Number of ligand-receptor complexes

. Formation is non-covalent and follows 1st order molecular kinetics

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18
Q

Affinity constant K

A

. Represents how readily ligand assoc. w/ receptor
. K = [LR]/[L][R]
. K = concentration of ligand when 50% receptor sites are bound
. Lower the K, higher the affinity to receptor

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19
Q

Alpha-1 adrenergic receptors

A

. Coupled to Gq protein, phospholipase C-IP3-mediated Ca signaling
. Cardiovascular: vascular smooth muscle contraction
. GI: dec. rate and strength of smooth muscle contractions (mediated by cAMP PKA dependent activation of K channels)
. Eye: dilation of pupil (mydriasis

20
Q

Alpha-2 adrenergic receptors

A

. Coupled to Gi protein, alpha subunit, dec. adenylate cyclase, cAMP, PKA
. Gi protein beta-gamma subunits inc. K channels
. Endocrine: stimulate gluconeogenesis, dec. insulin, inc. glucagon release
. GI: dec. rate and strength of smooth m. Contraction (mediated by Gi protein-induced reduction of cAMP
. CNS: located in presynaptic terminals as autoreceptors mediated neg. feedback of NE release (presynaptic inhibition)

21
Q

Beta adrenergic receptors

A

. Coupled to Gs protein
. Inc. adenylate cyclase
. Inc. cAMP
. Inc. PKA

22
Q

Beta-1 adrenergic receptors effect on systems

A

. Cardiovascular: inc. CO, HR, and contractile force of heart
. GI: inc. secretion thick viscous saliva

23
Q

Beta-2 adrenergic receptor effect on system

A

. Respiratory: dilation of bronchial smooth m. To open airways
. GI: dec. motility of visceral smooth muscle
. Endocrine: inc. glycogenolysis in adipose tissue

24
Q

Cholinergic receptors

A

. ACh receptors
. Muscarinic
. Nicotinic

25
Q

Muscarinic receptors

A

. Located on target organs
. M1-M5
. Activation produces excitatory or inhibitory response depending on target organ
. Activation of odd-numbered receptors leads to inc. intracellular Ca through IP3-DAG system
. Activation of even numbered receptors dec. cAMP and PKA

26
Q

Muscarinic receptors effect on systems

A

. Eye: contraction of pupil (miosis)
. Cardiovascular: SA node (dec. HR by M2-mediated activation of K channels), vasodilation of vessels
. Respiratory: constriction bronchial smooth muscle
. GI: inc. secretion thin saliva, inc. motility, inc. secretion of digestive enzymes
. Endocrine: inc. insulin secretion, inc. glycogen storage
. Sweat: inc. sweat
. Renal: contract bladder wall during urination

27
Q

Nicotinic receptors

A

. Always produces excitatory response in skeletal m. Or autonomic neuron
. Nicotinic-muscle (Nm/N1)
. Nicotinic-neural (Nn/N2)

28
Q

N1 receptors

A

. at motor end plate on skeletal muscle

. Voluntary contraction of skeletal m.

29
Q

N2 receptors

A

. Located on cell bodies of all postganglionic neurons (sympathetic and parasympathetic)
. Located in adrenal medulla
. Activation of postganglionic sympathetic and parasympathetic neurons
. Antagonists block synaptic transmission in sympathetic and parasympathetic nervous systems

30
Q

Signal transduction

A

. Neurotransmitters are hydrophilic and need receptor to cross lipid membrane
. Binding to receptor triggers series of events in cell that cause biological response

31
Q

Signal amplification

A

. Single activated enzyme can turn substrate molecules into product
. At each step, another application takes place
. Explains how neurotransmitters can be effective at extremely low concentration

32
Q

Types of signal transduction

A

. Receptors that are also ion channels
. Receptors that are protein kinases
. Receptors that interact w/ JAK kinases
. Receptors that are G protein coupled

33
Q

Receptors that are also on ion channels

A

. When NT binds to receptor, ion channel opens
. Permits diffusion of ion down their concentration gradient
. Ions entering cell can alter membrane potential and/or act as second messenger itself
. Generate biological response

34
Q

Receptors that are protein kinases

A

. Most commonly tyrosine kinase

. Protein phosphorylated by tyrosine kinase generates biological response

35
Q

Receptors that interact w/ JAK kinases

A

. Binding of ligand to receptor activates JAK
. JAK phosphorylated specific proteins
. Generates biological response

36
Q

Receptors that are coupled to G proteins

A

. Binding of NT to receptor activates G protein by substituting GTP for GDP
. Activated G protein binds to and opens ion channels or activates (or inhibits) a membrane bound enzyme
. Enzyme inc. or dec. generation of 2nd messenger inside cell
.2nd messenger activates a protein kinase that phosphorylates specific proteins that generate biological response

37
Q

Main second messengers

A 
.cAMP
.cGMP
. IP3
. DAG
. Ca (Ca-calmodulin)
38
Q

Cyclic AMP pathway

A

. G-binding regulatory protein (Gs) activates adenylyl cyclase (Gi inhibits adenylyl cyclase)
. Adenylyl cyclase converts Mg-ATP to cAMP
. Hydrolysis of GTP to GDP terminates activation
.cAMP binds to regulatory subunit on cAMP-dependent protein kinase to activate it
. Kinase phosphorylates many proteins to amplify biological response
.cAMP metabolized by phosphodiesterase (PDE) that concerts it to inactive metabolite (5’AMP subunit of protein kinase)

39
Q

Cyclic GMP pathway

A

. Generated by guanylyl cyclase
. Main target is cGMP-dependent protein kinase (PKG)
.cGMP directly activates several ion channels or ion pumps that participate in modulating cytoplasmic Ca levels in smooth muscle and sensory tissue
. Activation of ion channels directly by cGMP binding to from phosphorylation by PKG that alters cytoplasmic Ca
. Production regulated by activation of cytoplasmic or membrane localized form of GC

40
Q

GCs

A

. Targets of NO produced by endothelial cells

. Pathway mediates smooth muscle relaxation and neurotransmission

41
Q

IP3 and DAG pathway

A

. Gq activates membrane bound phospholipase C
. Catalyze breakdown of membrane PIP2 to DAG and IP3
. DAG activates PKC that phosphorylates proteins
. IP3 binds to IP3 receptor (ligand-gated ion channel) in ER to induce Ca release
. Result is inc. intracellular Ca

42
Q

How Ca induces cellular responses

A

. Binding to calmodulin
. Combining to other Ca-binding proteins
. Directly binding to and affecting target proteins

43
Q

Ways to inc. intracellular Ca

A

. Directly through Ca channels in surface membrane

. Release from intracellular Ca stores

44
Q

Main intracellular Ca store is ___

A

. In the ER

45
Q

Ca release from ER

A

. Through ryanodine and IP3 ligand-gated receptors
. Ryanodine: more specialized, involved in excitation-contraction coupling in muscle and Ca induced Ca release in neurons
. IP3R: more ubiquitous role, present in all types of cells

46
Q

AChE inhibitors

A

. Used for glaucoma, inc. GI motility, and myasthenia Gravis

47
Q

Disposition of NE neurotransmitter

A

. Presynaptic: uptake by active pump uptake-1 (inhibited by cocaine and tricyclic antidepressants), after uptakes by presynaptic neuron, NE metabolized by MAO enzyme
. Target cells: uptake-2 pump (not cocaine sensitive), after uptake in postsynaptic cell, NE metabolized by COMT
. Diffusion: detectable in plasma

Physio (62 decks)

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